Conventional refrigeration cycle apparatuses include: an outdoor unit that has a compressor and a heat source-side heat exchanger; an indoor unit that has a use-side heat exchanger and a throttling apparatus; and refrigerant piping that connects these, and are configured such that the compressor, the heat source-side heat exchanger, the throttling apparatus, and the use-side heat exchanger are connected by piping (see Patent Literature 1, for example).
In recent years, from a viewpoint of environmental protection, hydrofluorocarbon (HFC) refrigerants (fluorocarbons that do not contain chlorine), which have an ozone depletion coefficient of zero, R-404A refrigerants (blended refrigerants of R-125, R-134a, and R-143a), R-410A refrigerants (50% by weight R-32 and 50% by weight R-125), etc., have been used as refrigerants that are sealed inside refrigeration cycle apparatuses. If a user upgrades from a refrigeration cycle apparatuses that uses an R-404A refrigerant to a refrigeration cycle apparatuses that uses an R-410A refrigerant, for example, then it is conceivable that crossover piping of the refrigeration cycle apparatus that has been used until then could be reused as the crossover piping for the new refrigeration cycle apparatus from a viewpoint of simplicity of construction work and reductions in parts costs.
However, the working pressure of R-410A is higher than the working pressure of R-404A. Thus, if crossover piping from a refrigeration cycle apparatus that uses an R-404A refrigerant is reused as crossover piping for a refrigeration cycle apparatus that uses an R-410A refrigerant, then the pressure of the refrigerant may rise if the temperature of the refrigerant rises due to an increase in outside air temperature particularly under conditions in which the refrigeration cycle apparatus is stopped due to a power outage, etc., in a state in which refrigerant has accumulated inside the crossover piping, and there has been a risk that the pressure of the refrigerant may exceed a pressure tolerance reference value of the crossover piping. Because of that, it has been necessary to change the crossover piping to thicker piping. In addition, when refrigeration cycle apparatuses are used in freezing and refrigeration of display cases that are installed in shops such as convenience stores or supermarkets, outdoor units are often installed in locations that are distant from indoor units, and the entire length of the crossover piping may reach 100 m. Thus, because installation of crossover piping at the site becomes complicated and material cost of the piping is high, some problems have been that installation time is longer, and that installation costs are also increased.
In consideration of such conditions, conventional refrigeration cycle apparatuses have been proposed that include: liquid-side crossover piping and gas-side crossover piping that connect an outdoor unit and an indoor unit; liquid-side refrigerant piping that connects a condenser and the liquid-side crossover piping; gas-side refrigerant piping that connects a compressor and the gas-side crossover piping; first connection piping that extends from the liquid-side refrigerant piping or the liquid-side crossover piping; second connection piping that extends from the gas-side refrigerant piping or the gas-side crossover piping; a refrigerant storage tank that stores the refrigerant inside the crossover piping, an intake side thereof being connected to the first connection piping, and a discharge side thereof being connected to the second connection piping; a first check valve that is disposed on the first connection piping, and that allows the refrigerant to flow only in a direction of suction toward the refrigerant storage tank; a first electromagnetic valve that is disposed on the first connection piping, and that shuts off during passage of electric current; and a second electromagnetic valve that is disposed on the second connection piping, and that opens during passage of electric current (see Patent Literature 2, for example).
In the conventional refrigeration cycle apparatus that is described in Patent Literature 2, even if operation is shut down due to a power outage, etc., in a state in which refrigerant is accumulated inside the liquid-side crossover piping, the refrigerant inside the liquid-side crossover piping can be stored in the refrigerant storage tank temporarily, enabling the liquid refrigerant inside the liquid-side crossover piping to be removed. Thus, even if the refrigerant is a high-pressure refrigerant, and the external air becomes hot, problems with pressure tolerance in the liquid-side crossover piping do not arise. Because piping that has a pressure tolerance reference value for low-pressure refrigerant can thereby be used for the liquid-side crossover piping even if the refrigerant is changed from a low-pressure refrigerant to a high-pressure refrigerant, installation time can be shortened, and installation costs can be reduced.
[Patent Literature 1]
International Publication No. WO/2004/013549
[Patent Literature 2]
Japanese Patent No. 4687710 (Gazette)
However, in the conventional refrigeration cycle apparatus that is described in Patent Literature 2, because there is no mechanism for removing the gaseous refrigerant from inside the refrigerant storage tank when the refrigerant inside the liquid-side crossover piping is stored in the refrigerant storage tank, the refrigerant inside the liquid-side crossover piping could not be collected satisfactorily. Thus, the refrigerant may remain inside the liquid-side crossover piping, and there is a possibility that the pressure inside the liquid-side crossover piping may exceed the pressure tolerance reference value.
Furthermore, if an attempt is made to collect the refrigerant inside the liquid-side crossover piping without removing the gaseous refrigerant from inside the refrigerant storage tank, one problem has been that a large-capacity vessel is required as the vessel for the refrigerant storage tank, increasing vessel costs, and also increasing installation area.